On Mon, Sep 30, 2019 at 03:06:15PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 16, 2019 at 06:41:21AM -0700, [email protected] wrote:
> > +static bool is_first_topdown_event_in_group(struct perf_event *event)
> > +{
> > + struct perf_event *first = NULL;
> > +
> > + if (is_topdown_event(event->group_leader))
> > + first = event->group_leader;
> > + else {
> > + for_each_sibling_event(first, event->group_leader)
> > + if (is_topdown_event(first))
> > + break;
> > + }
> > +
> > + if (event == first)
> > + return true;
> > +
> > + return false;
> > +}
>
> > +static u64 icl_update_topdown_event(struct perf_event *event)
> > +{
> > + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> > + struct perf_event *other;
> > + u64 slots, metrics;
> > + int idx;
> > +
> > + /*
> > + * Only need to update all events for the first
> > + * slots/metrics event in a group
> > + */
> > + if (event && !is_first_topdown_event_in_group(event))
> > + return 0;
>
> This is pretty crap and approaches O(n^2); let me think if there's
> anything saner to do here.
This is also really complicated in the case where we do
perf_remove_from_context() in the 'wrong' order.
In that case we get detached events that are not up-to-date (and never
will be). It doesn't look like that matters, but it is weird.
